Alloy



Patented Feb. 15, 1938 UNITED STATES armor Birger Egeberg, Merlden, Com,and Boy W.

Tindula, Buffalo, N. Y., asslgnors to Internatlonal Silver Company,Meriden, Com, a corporation of New Jersey No Drawing. Otisina 1934,Serial No. 759,053. plication April 20, 1937,

14 Claims.

.This invention relates to alloys and this application is a division ofapplication Serial No. 759,053 filed December 24, 1934.

The object of the invention generally is a tarnish and corrosionresistant alloy which may be readily cold worked, may be melted and castmore easily than prior non-tarnish and non-corrosive alloys, and may beeconomically produced, and particularly an alloy adapted for use in themanufacture of tableware and various kinds of hardware where a completeor substantially complete resistance to weak organic acids, saltsolutions, and organic sulphur compounds is necessary, or where superiorresistance to many strong mineral acids, such as sulphuric and nitric,is desired.

A further object of the invention is an alloy which, being resistant totarnish and corrosion by all ordinary materials found in foodstuffs,such as sulphur compounds, salt solutions, and.

weak organic acids, requires no superimposed non-tarnish coating for usein the manufacture of tableware, and which is characterized generally byits favorable chemical resistance, desirable physical properties, easeof cold working, ease of polishing to a high. luster, ease of treatment,low melting point, ease of production, and lowcost.

To these ends we have produced an alloy embodying chromium, nickel,copper, zinc and iron, all in substantially complete solid solution, andin proportions, coupled with special heat treatment whendesired, toendow the same with the desired characteristics above indicated.

The individual elements of the alloy may vary over a limited andprescribed range in percentage but the amounts of nickel, chromium, andiron must be carefully controlled and proportioned and the copper, andzinc contents carefully proportioned and balanced against the nickel,chromium and iron contents, with carbon and other impurities kept belowpredeter mined values.

In order to produce the alloy of our invention which offerssubstantially complete resistance to tarnish and corrosion by householdreagents, foodstuffs, weak organic acids, sulphur com- 1 pounds, salineor industrial atmospheres, and

corrosive vapors, we find it necessary that about a one atom (or over)of every eight atoms in the alloy be of chromium (that is at leastapproximately 11 per cent by weight of chromium in solid solution) andfurthermore that the other elements be so proportioned that theannealing treatment given will bring this amoun 01' ch 0- l applicationDecember 24,

Divided and this ap- Serial No. 137,913

mium into solid solution. For resistance to the more corrosivematerials, such as nitric acid we have found a higher percentage ofchromium than that which corresponds to the .125 atomic fraction (about11% by weight) to be of great value, as for example up to 1'7 per centand higher. In alloys for use in applications not involving acidcorrosion, smaller proportions of chromium in solid solution may beemployed, as for example as low as four or five per cent.

The nickel content serves to bring the other constituents of the alloyinto uniform solid solution and preferably sufficient nickel must beincorporated for this purpose. It also substantially, along withchromium, favorably affects the. degree of resistance to varioustarnishing and corroding media by affecting the solubility of chromiumat various temperatures, and tends to improve the workability and givesomewhat increased luster in the polished state, but these advantagesare somewhat offset by increase in melting point, greater cost, darkercolor, etc. Ac-

cordingly, the nickel content is kept as low as is permissible, thoughit may vary from forty to seventy per cent by weight.

By incorporating zinc not only may the proportion of copper be therebyreduced, but the alloy becomes mdowed with certain of the specialproperties and characteristics above described. For example, while themelting point of pure nickel may be progressively lowered about 50 F.for each 10% of copper alloyed with it, 10% of zinc will lower' themelting point by approximately 125' F. Thus with a given chromium andnickel content the substitution of 10% zinc in place of 10% of copperproduces an alloy with a melting point F. lower. This greatlyfacilitates melting and makes it possible to obtain a much more fluidmelt and better ingots. The substitution of 5% to 10% zinc also resultsin an alloy with greater softness on annealing the cold worked alloy, 3,better surface on alloys whichof 10% and our alloy with a component ofas much as 15% to 20% of zinc still possesses a limited degree of coldworkability. For best results we prefer to use with an alloy contain-'tlon by weight and preferably .that by alloying manganese and zinc withcopper. (and the other elements) and for alloys of the higher chromiumrange limiting the copper to less than about 30%, with the correspondingproportions of nickel, chromium and iron above described, superior orcomplete resistance of the alloy to tarnish and corrosion bysulphur.compounds and organic acids is secured. The presence of copperalso aids in the alloying of the zinc with the other elements. Thecopper content should not be less than 5% of the composiis substantiallylarger (around 15%), 5% to 20% for alloys of the higher chromium range,and in alloys oi' the lower chromium range copper maybe alloyed up to alimit of about 55% by weight.

Our alloy is essentially non-ferrous, but we have found it an advantage,to include in the alloy a small percentage of iron, since it increasesthe solubility of chromium'for a given nickel content and promotes amore homogeneous structure, or to put it difierently it also reduces thenecessary quantity of nickel by an amount greater than the'iron content.Further, it is beneficial in that the copper content is reduced to apoint where the corrosive resistant properties of the alloy are notlowered by the copper. It also renders possible a substantial reductionin cost of producing the alloy, since ferrochrome is much cheaperthanchromium metal and also is more easy to introduce into the meltbecause of its lower melting point. In this respect ferrochrome has adistinct advantage over pure chrome in that it minimizes evaporationlosses during melting especially that of alnc. The iron content of themelt, however, is best limited to that which results from using ferroalloys as the original source of chromium, because the further additionof iron causes reduction in amount of those elements (copper and zinc)which assure the desired low annealing and melting points and otherwisecon tribute to the advantages above described. The iron content shouldnot exceed ten per cent by weight and preferably should be substantiallylower. We have obtained particularlygood results with iron content offrom 2% to 6% in a1- it must be kept below the upper limits describedbelow because it may remove a considerable amount of chromium fromefiective service in preventing tarnish, thus making a greater chromiumcontent necessary than if it were not present. It tends to form a hardand insoluble constituent within the alloy that greatly impairsmalleabllity and ductibility which can only be partly counteracted byhigher nickel contents,

tions less than the below mentioned amounts,

increases the frictional wear resistance of the alloy and isconsequently detrimental from the standpoint of ease of polishing andthe amount of labor involved. We have found that the carbon contentshould not exceed 0.5 per cent at 35% nickel, .12 per cent at 50%nickel, .15 per cent at 60% nickel, or .20 percent at 70% nickel.

The following are examples of embodiments of our invention:

CHEMICAL Answers Group I Ni Cr Cu Zn Fe Si 0 09.5 11.7 7.2 5.5 4 s .1410 00.2 12.4 i 12.2 8.3 0 a .07 05 53.2 15. 5 13.0 10.0 7 0 .32 07 55.210.9 11.2 9.5 7 2 .19 04 50.0 20.5 3.7 5.5 s 9 .33 07 Group II 52.9 10.915.0 14.9 5.0 .24 00 51.0 11.1 17.5 14.0 as 15 .074 51. 1 12. 3 14 9 151 a 2 .35 .040 51. 2 14. 1 19. 5 14. 0 1. 0 5 .22 055 Group III 50. 0 4.7 20 22.3 2 1 0. 25 0. 04 50.2 7.4 102 1&7 4.3 0.27- 0.04 35 5. 5 a is 30. a 0.1

These examples of the alloy show' a range in proportions of chromiumfrom around 4 to 17 per cent, nickel 36 to '70 per cent, zinc from 2 to20 per cent, iron 1 to per cent and. the balance copper in excess of 5per cent with the carbon content limited as described above.

Group I of the examples includes alloys whose condition of completeimmunity to tarnish or corrosion by mayonnaise and vinegar or any otherordinary household agent is obtained by any annealing treatment ofcommercial duration. These alloys may also be used in the castcondition, after any commercial furnace annealing treatment or aftersoldering, etc.', with substantially complete immunity to tarnish orcorrosion.

also to prolonged heating at temperatures somewhat below 1600 F.

Group II includes alloys which by means of high temperature finalannealing treatment (generally from 1900 F. up followed by rapidcooling) can be rendered completely immune to tarnish or corrosion bymayonnaise and vinegar. After final anneallngs carried outat lower tem-'peratures, alloys in this class are very slightly attacked by thesematerials. For complete resistance to milder conditions as atmospherictarnish, corrosion by salt spray, or tarnish by egg or hydrogensulphide, this high annealing temperature will not be necessary.

Group III includes alloys which are not completely immune to attack bymayonnaise and vinegar but may be somewhat improved in this respect byheat treatment similarto the heat treatment for Group 11. However, anysuch attack that does take place is much slower and not as severe aswould take place on any relatively inexpensive alloys now known to theart which do not contain chromium. At the same time, these alloys inGroup III are substantially immune to atmospheric tarnish, corrosion bysalt spray, or tarnish by egg or hydrogen sulphide,

- In the practical production of the alloy it is impossible to avoidtraces of one or more other elements being present as impurities in theessential elements making up the charge or extracted. from the furnacelining or slag, such for example as traces of silicon, carbon, cobalt,tin, aluminum, etc., but it is understood that such impurities asdescribed above with respect to carbon are reduced to the lowestpracticable value.

Small additions of magnesium to the alloy are harmless, and preferably0.1 per cent of magnesium as a copper. alloy is added to the melt justbefore pouring to remove oxygen and other harmful gases. For example, inorder to produce asound ingot free ofexcessive blowholes, it isdesirable to add to the melt a small amount of magnesium, aluminum,calcium, barium, lithium, or other strongly reactive metal or alloy. Thepreferred practice is to add about one-half pound of acopper alloycontaining 20% magnesium to every 100 pounds of total melt one or twominutes before casting.

Any suitable method may be utilized-for bringing the constituents of thealloy of our invention into a melt of the desired proportions and thefollowing is merely suggestive of one procedure. It is desirable to usea furnace or crucible lined with a material free or nearly freeofcarbon. It is very important that the metal come only in contact withnon-carbonaceous materials during the melting period.

Chromium may be added in the form of low' melting point addition alloyssuch as a 50-50 chrome-nickel alloy, or 9. 38-37-25 chromiumnickel-copperalloy, but low carbon ferrochrome may be added directlytothe melt without formation of a lower melting alloy previously. Themethod of adding the various ingredients to the melt of our inventionmay be varied in any way provided the ingot analyses produced be withinthe limits described above.

After the ingot casting is obtained it may be converted into strip,sheet, or any type of hollowware, flatware, hardware'or ornamentalarticles in essentially a similar manner to that now used by the art,viz: hot working, cold working and annealing. Cold rolling and annealingschedules will vary considerably for the various alloys, but in generalit can be stated that most of the alloys embodied in our invention willwithstand at least 50% reduction in thickness by cold rolling betweensuccessive annealings, and can be made sufliciently soft for furtherworkingby annealing between 1600 and 2000" F.

We have thus set forth the relative proportions or our alloy and havegiven certain limited ranges in proportions together with certainspecific examples and it is understood that the proportions may bevaried within the limited range described depending on the particularuse to which the alloy is to be put. Where an alloy of maximumworkability, luster, and complete tarnish and corrosion resistance isdesired, the higher chromium and nickel ranges are to be 'used. For anymaterial which is to be soldered, brazed or welded into finishedarticles an alloy of our invention containing more than 54% nickel and11% chromium by weight should be used.

An alloy within the Group I of our invention is suitable, as indicated,for use in the cast condition for tarnish and corrosion resistance, and,since mechanical workability is not a factor here, we may add about 1%of silicon to the alloy for improved sharpness in casting.

For manufacture of cutlery articles and other materials which requirecomplete) or essentially complete non-corrosive and'non-tarnishproperties, and where the material can be annealed at a high temperaturejust before or after final fabricating processes either of theembodiments Groups I or II can be used. For example, for manufactureinto spoons, forks, knives, and other tableware an alloy of ourinvention containing more than 48% nickel, more-than 11% chromium and nogreater than 30% copper is preferable. The final annealing treatmentbefore or after fabrication into final form should consist of heatingthe alloy to a temperature between about 1900 and 2100 F. and coolingrapidly.

For manufacture of hardware and other articles where extreme corrosionresistance is not as important as strength, lower cost, and ease ofmanufacture, any of the alloys within the limits to 10% iron, 2 to 20%zinc and the balance copper, in excess of 5%, with traces of otherelements including a small trace of carbon.

3. A cold workable, low melting point alloy having non-tarnishcharacteristics, consisting of chromium, nickel, copper, iron and zinc,wherein the chromium content is 10 to 20%, nickel 45m 10%, zinc 2 to20%, iron 1 to 10% but not in excess of 60% of the chromium content, andthe balance copper in excess of 5% and not greater ing a small trace ofcarbon.

4. A cold workable, low-melting point alloy having non-tarnishcharacteristics, consisting of nickel, chromium, copper, iron, and zinc,wherein the'chromium content is 4'to 10%, nickel 36 to 60%, zinc 2-to20%, iron 1 to 10% but not in' excess of 60% of the chromium content,and the balance copper in excess of 13% and not greater than 55%, withtraces of other elements including carbon with the carbon not in excessof 0.2%.

5. An alloy of the character set forth in claim 1 wherein the ironcontent is from 40 to of the chromium content.

6. A cold workable, low melting point alloy having non-tarnishcharacteristics consisting of 5.4 to 70% nickel, 11 to 20% chromium, 5.8to 25% copper, 1.5 to 20% zinc, l to 10% iron, but not in excess ofsix-tenths the chromium content, with traces of other elements includingcarpen with the carbon not in excess of 0.2%.

than 30%, with traces of other elements includtween 1900 F. and themelting point consisting.

of 11 to 15% chromium, 48 to 54% nickel, 5.8 to 30% copper, 1 to ofiron, but not in excess six-tenths the chromium content.

10. A cold workable, non-tarnish alloy consisting of 50 to 55% nickel,around 11% chromium, 10 to zinc, 1 to 10% iron but not in excess of 60%of the chromium content, and the balance copper in excess of 5%, withtraces of other elements including carbon with the carbon not exceeding0.2%.

11. A non-tarnish, cold workable alloy consisting bi 4 to 10% chromium,35 to 60% nickel, 10 to zinc, 1 to'10% iron but not in excess of 60% ofthe chromium content, and the balance copper, zinc and iron in theapproximate proportions of 50.2 nickel, 7.4 chromium, 19.2 copper, 18.7zinc, 4.3 iron with traces of other elements including carbon with thecarbon not exceeding 0.2%.

, BIRGER EGEBERG.

ROY W. EINDULA.

5 of six-tenths the chromium content, and. the recopper in excess of 5%,with traces of other 5 maincler zinc between 6 to 20% and traces ofelements including carbon with the carbon not other elements includingcarbon with the carbon exceeding 0.2%. not in excess of 0.2%. p 12. Anon-tarnish alloy of nickel, chromium,

8. A cold workable, non-tarnish, low melting copper, zinc and iron inthe approximate proporpoint alloy which consists of chromium, nickel,tions or 53.2 nickel, 15.5 chromium, 13.0 copper, 19 copper, iron andzinc in the proportions of 4 to 10.9 zinc, 1.0 iron with traces of otherelements 20% chromium, to 70% nickel, 6 to 18% zinc, including carbonwith the carbon not exceeding and 1 to 10% iron, but not in excess ofsix-tenths 0.2%. the chromium content, with the remainder cop- 13. Anon-tarnish alloy consisting of nickel,

15 per in excess 01' 5% and traces of carbon not in chromium, copper,zinc and iron in the approxi- 5 excess of 0.2%. mate proportions of 51.0nickel, 11.1 chromium,

9. An alloy of the character set forth in claim 17.5 copper, 14.6 zincand 5.6 iron with traces of 3 wherein the chromium content is from 10 toother elements including carbon with the carbon 16% by weight, thenickel content is from to not exceeding 0.2%. 20 and the iron content isfrom one-eighth to 14.-An alloy consisting of nickel, chromium, 20

, CERTIFICATE OF CORRECTION.

Patent No. 2,10 ,ou February 15, 19

' BIRGER EGEBERG, ET AL. 1

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 1first column, line 15, claim 8, before 'oarbon" insert the words otherelements including carbon with the; and that the said Letters Patentshould be read with this correction therein that the same may conform tothe record of the case in the Patent Office... I

Signed and sealed this 12th day of April, A. D. 1958.

Henry Van Ar sdale iSeal) I Acting commissioner of Patents.

tween 1900 F. and the melting point consisting.

of 11 to 15% chromium, 48 to 54% nickel, 5.8 to 30% copper, 1 to ofiron, but not in excess six-tenths the chromium content.

10. A cold workable, non-tarnish alloy consisting of 50 to 55% nickel,around 11% chromium, 10 to zinc, 1 to 10% iron but not in excess of 60%of the chromium content, and the balance copper in excess of 5%, withtraces of other elements including carbon with the carbon not exceeding0.2%.

11. A non-tarnish, cold workable alloy consisting bi 4 to 10% chromium,35 to 60% nickel, 10 to zinc, 1 to'10% iron but not in excess of 60% ofthe chromium content, and the balance copper, zinc and iron in theapproximate proportions of 50.2 nickel, 7.4 chromium, 19.2 copper, 18.7zinc, 4.3 iron with traces of other elements including carbon with thecarbon not exceeding 0.2%.

, BIRGER EGEBERG.

ROY W. EINDULA.

5 of six-tenths the chromium content, and. the recopper in excess of 5%,with traces of other 5 maincler zinc between 6 to 20% and traces ofelements including carbon with the carbon not other elements includingcarbon with the carbon exceeding 0.2%. not in excess of 0.2%. p 12. Anon-tarnish alloy of nickel, chromium,

8. A cold workable, non-tarnish, low melting copper, zinc and iron inthe approximate proporpoint alloy which consists of chromium, nickel,tions or 53.2 nickel, 15.5 chromium, 13.0 copper, 19 copper, iron andzinc in the proportions of 4 to 10.9 zinc, 1.0 iron with traces of otherelements 20% chromium, to 70% nickel, 6 to 18% zinc, including carbonwith the carbon not exceeding and 1 to 10% iron, but not in excess ofsix-tenths 0.2%. the chromium content, with the remainder cop- 13. Anon-tarnish alloy consisting of nickel,

15 per in excess 01' 5% and traces of carbon not in chromium, copper,zinc and iron in the approxi- 5 excess of 0.2%. mate proportions of 51.0nickel, 11.1 chromium,

9. An alloy of the character set forth in claim 17.5 copper, 14.6 zincand 5.6 iron with traces of 3 wherein the chromium content is from 10 toother elements including carbon with the carbon 16% by weight, thenickel content is from to not exceeding 0.2%. 20 and the iron content isfrom one-eighth to 14.-An alloy consisting of nickel, chromium, 20

, CERTIFICATE OF CORRECTION.

Patent No. 2,10 ,ou February 15, 19

' BIRGER EGEBERG, ET AL. 1

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 1first column, line 15, claim 8, before 'oarbon" insert the words otherelements including carbon with the; and that the said Letters Patentshould be read with this correction therein that the same may conform tothe record of the case in the Patent Office... I

Signed and sealed this 12th day of April, A. D. 1958.

Henry Van Ar sdale iSeal) I Acting commissioner of Patents.

